Pancreatic cancer is highly lethal. It has been estimated that 37,170 new cases and 33,370 deaths resulted from pancreatic cancer in the United States in 2007. Pancreatic cancer has one of the worst prognoses of all human malignancies. Existing treatments, such as surgical resection and chemotherapy, have poor survival rates. The 5-year survival rate for patients diagnosed after the occurrence of metastases is very low, and has not improved since 1973. Pancreatic cancer is a multistep, progressive disease characterized by genetic abnormalities, altered signaling pathways, and loss of cellular regulatory functions. Metastatic cells in bone, lungs, lymph nodes, and other organs cause recurrent cancer and are the major cause of death. An effective targeted therapy could be of great benefit for patients with advanced or metastatic tumors from pancreatic cancer.
Three distinct precursor lesions of pancreatic cancers have been identified: mucinous cystic neoplasms, intraductal papillary mucinous neoplasms (IPMNs), and pancreatic intraepithelial neoplasia (PanINs). PanINs progress from early lesions, PanIN-1A and1B (hyperplasia), through PanIN-2 lesions, and then to PanIN-3 lesions (carcinoma in situ) (2). Pancreatic ductal adenocarcinoma (PDAC) accounts for 90 percent of pancreatic cancers.
The molecular mechanisms underlying pancreatic cancers have been extensively investigated. Several tyrosine kinase growth factor receptors and their ligands are overexpressed, including epidermal growth factor (EGF), epidermal growth factor receptor (EGFR-1) and its ligands, transforming growth factor-alpha (TGF-α), the TGF-β superfamily of serine-threonine kinase receptors and their ligands, the fibroblast growth factor family, the insulin-like growth factor family, hepatocyte growth factor, platelet-derived growth factor, and vascular endothelial growth factor. This overexpression influences tumor cell growth, differentiation, invasion, metastasis, and angiogenesis, factors that are associated with tumor aggressiveness and short survival periods even following tumor resection.
Gonadotropin-releasing hormone (GnRH, a decapeptide, also called luteinizing hormone releasing hormone or LHRH), and the LHRH receptor molecule (LHRHR) are best known for their functions in reproduction. They also play a role in the negative autocrine/paracrine regulatory system of cell proliferation in several malignant tumors, including cancers of the endometrium, ovary, breast, prostate, endometrium, and melanomas. About 50% of breast cancers and 80% of ovarian and endometrial cancers express high affinity binding sites for LHRH. In these cancers in vitro proliferation has been inhibited by agonist or antagonist analogues of LHRH. The role of LHRH and LHRHR in pancreatic cancer has received less attention See H. Friess et al., “LH-RH receptors in the human pancreas. Basis for antihormonal treatment in ductal carcinoma of the pancreas,” Int. J. Gastrointestinal Cancer, vol. 10, pp. 151-159 (1991); and B. Szende et al., “Localization of receptors for luteininizing hormone-releasing hormone in pancreatic and mammary cancer cells,” Proc. Natl. Acad. Sci. USA, vol. 88, pp. 4153-4156 (1991).
A major problem in most forms of cancer chemotherapy is the severe toxicity most such drugs also have against rapidly-dividing cells in healthy tissues. These side effects often result in dose reduction, treatment delay or discontinuance of therapy. Targeted drug delivery systems have been developed to try to circumvent these side effects, using targeting agents such as receptor ligands, sugars, lectins, antibodies, antibody fragments, hormones, and hormone analogues. For example, conjugates of lytic peptides with either LH or LHRH (or analogs) have been used against cancers, such as breast cancers and prostate cancers, that express LH receptor or LHRH receptor on their membranes. See C. Leuschner et al., “Membrane disrupting lytic peptides for cancer treatments,” Curr. Pharm. Des., vol. 10, pp. 2299-310 (2004); U.S. Pat. No. 6,635,740; W. Hansel et al., “Destruction of breast cancers and their metastases by lytic peptide conjugates in vitro and in vivo,” Mol. Cell. Endocrinol., vol. 260-262, pp. 183-9 (2007); U.S. Pat. No. 6,635,740; and C. Leuschner et al., “Targeting breast and prostate cancers through their hormone receptors,”Biol. Reprod., vol. 73, pp. 860-5 (2005).
Numerous mechanisms have been suggested for the effects of LHRH and LHRHR. One proposed mechanism involves activation of nuclear factor-kappa B (NF-kB) in ovarian cancer cells. NF-kB is a regulatory transcription factor involved in controlling cell growth, differentiation, survival, and cell cycle progression. In normal cells NF-kB is not constitutively expressed, except in proliferating T cells, B-cells, thymocytes, monocytes, and astrocytes. There is evidence to suggest that NF-kB plays a role in the growth and chemoresistance of pancreatic cancer: (1) NF-kB has been found to be constitutively active in pancreatic cancer cells, but not in immortalized, nontumorigenic pancreatic ductal epithelial cells. (2) Active NF-kB has been reported in pancreatic cancer xenografts in mice. (3) NF-kB has been reported to promote pancreatic cancer growth by inhibiting apoptosis. (4) The NF-kB-mediated gene product cyclin D1 is overexpressed in human pancreatic cancer tissue, and has been inversely correlated with patient survival. (5) NF-kB has been associated with gemcitabine resistance in pancreatic cancer.
There is an unfilled need for strong inhibitors of NF-kB to treat or prevent pancreatic cancer and other cancers in which the cancer cell membranes express receptors for one or more of LHRH, LH, or CG.
Epidemiologic and animal studies have shown that compounds that are naturally present in some foods can help prevent cancer. Some of these compounds have further shown significant anti-tumor activity, both in vitro and in preclinical testing. There is an increasing interest in plant-derived chemicals that have anti-cancer activity with low toxicity. Curcumin (diferuloylmethane), a phytochemical present in turmeric (Curcumin longa), has been reported to have potent anti-proliferative and pro-apoptotic effects on cancer cells in vitro. In murine models, curcumin has suppressed carcinogenesis of the skin, the breast, the colon, and the liver. Curcumin has been shown to suppress NF-kB activity. Curcumin is pharmacologically safe, but it has low solubility in water and therefore has poor bioavailability by oral administration, and cannot be administered intravenously. Orally-administered curcumin has, nevertheless, been reported to potentiate the effect of the chemotherapeutic agent Gemcitabine in mice pancreatic cancer models. See M. Kuo et al., “Curcumin, an antioxidant and anti-tumor promoter, induces apoptosis in human leukemia cells,” Biochim. Biophys. Acta, vol. 1317, pp. 95-100 (1996); S. Aggarwal et al., “Inhibition of growth and survival of human head and neck squamous cell carcinoma cells by curcumin via modulation of nuclear factor-kappaB signaling,” Int. J. Cancer, vol. 111, pp. 679-92 (2004); P. Limtrakul et al., “Inhibitory effect of dietary curcumin on skin carcinogenesis in mice,” Cancer Lett., vol. 116, pp. 197-203 (1997); M. Huang et al., “Effect of dietary curcumin and dibenzoylmethane on formation of 7,12-dimethylbenz[a]anthracene-induced mammary tumors and lymphomas/leukemias in Sencar mice,” Carcinogenesis, vol. 19, pp. 1697-700 (1998); J. Kim et al., “Chemopreventive effects of carotenoids and curcumins on mouse colon carcinogenesis after 1,2-dimethylhydrazine initiation,” Carcinogenesis, vol. 19, pp. 81-5 (1998); S. Chuang et al., “Curcumin-containing diet inhibits diethylnitrosamine-induced murine hepatocarcinogenesis,” Carcinogenesis, vol. 21, pp. 331-5 (2000); S. Aggarwal et al., “Curcumin (diferuloylmethane) down-regulates expression of cell proliferation and antiapoptotic and metastatic gene products through suppression of kappa B alpha kinase and Akt activation,” Mol. Pharmacol., vol. 69, pp. 195-206 (2006); A. Kunnumakkara et al., “Curcumin potentiates antitumor activity of gemcitabine in an orthotopic model of pancreatic cancer through suppression of proliferation, angiogenesis, and inhibition of nuclear factor-kappaB-regulated gene products,” Cancer Res. vol. 67, pp. 3853-61 (2007).
In Phase II clinical trials in patients with advanced pancreatic cancer, orally-administered curcumin was reported to have only limited effect, and to have poor bioavailability. “Clinical biological activity” was reported for only 2 of 21 patients, consisting of a brief but marked period of tumor regression in one patient, and a “stabilization” of the disease for 18 months in the other patient. See N. Dhillon et al., “Phase II clinical trial of curcumin in patients with advanced pancreatic cancer,” J. Clin. Onco., vol. 24, pp. 14151 ff (2006); see also published United States patent application publication no. 2007/0270464.
S. Mishra et al., “Design, development and synthesis of mixed bioconjugates of piperic acid-glycine, curcumin-glycine/alanine and curcumin-glycine-piperic acid and their antibacterial and antifungal properties,” Bioorganic & Medicinal Chemistry, vol. 13, pp. 1477-1486 (2005) discloses the synthesis of the curcumin conjugates named in the paper's title, and the use of those conjugates against certain bacteria and fungi.
S. Mishra et al., “Differential apoptotic and redox regulatory activities of curcumin and its derivatives,” Free Radical Biology & Medicine, vol. 38, pp. 1353-1360 (2005) discloses several derivatives of curcumin, and the use of those derivatives to induce apoptosis in rat histiocytoma cells.
S. Dubey et al., “Design, synthesis and characterization of some bioactive conjugates of curcumin with glycine, glutamic acid, valine and demethylenated piperic acid and study of their antimicrobial and antiproliferative properties,” Eur. J. Medicinal Chem., vol. 43, pp.1837-1846 (2008) discloses the synthesis of mono- and di-esters of curcumin with the moieties named in the paper's title, and the use of those mono- and di-esters against certain bacteria, fungi, and human cancer cell lines.
A 15-amino acid segment of the beta chain of chorionic gonadotropin (βCG) conjugated to a lytic peptide (e.g., βCG-Phor21 (ala)) has been shown to target and destroy prostate and breast cancer cells. See J. Lee et al., J. Pharmacokinetics and Pharmacodynamics, vol. 60, pp. 1-8 (2008); W. Hansel et al., “Conjugates of lytic peptides and LHRH or BetaCG target and cause necrosis of prostate cancers and metastases,” Mol. Cell. Endocrinol., vol. 269, pp. 26-33 (2007); and (3) W. Hansel et al., “Destruction of breast cancers and their metastases by lytic peptide conjugates in vitro and in vivo,” Mol. Cell. Endocrinol., vol. 260-262, pp. 183-9 (2007).
S. Dutta et al., “Enhanced antioxidant activities of metal conjugates of curcumin derivatives,” Metal Based Drugs, vol. 8, pp. 183-188 (2001) discloses certain curcumin derivatives and copper conjugates, and their ability to scavenge free radicals.
J. Shim et al., “Hydrazinocurcumin, a novel synthetic curcumin derivative, is a potent inhibitor of endothelial cell proliferation,” Bioorganic & Medicinal Chemistry, vol. 10, pp. 2987-2992 (2002) discloses the activity of curcumin and certain derivatives against angiogenesis.
Published United States patent application publication no. 2007/0060644 discloses certain curcumin derivatives, and their use against certain conditions including Alzheimer's disease, diabetes, cancer, inflammation, and other conditions.
U.S. Pat. No. 5,861,415 discloses anti-oxidant, anti-inflammatory, antibacterial, antifungal, antiparasitic, anti-mutagen, anticancer and detoxification properties of curcuminoids, including curcumin, demethoxy curcumin and bis demethoxy curcumin.
U.S. Pat. No. 5,891,924 discloses the use of curcumin to inhibit the activation of NfkB transcription factor, for example to treat toxic/septic shock or graft-versus-host reaction.
Published international patent application WO/2002/002582 discloses curcumin derivatives with improved water solubility, in which the curcumin is linked to a mono, oligo, or polysaccharide, and the use of these curcumin derivatives against cancer, chronic-inflammatory diseases, and diseases associated with a retrovirus infection.
It has been reported that uterine fibroids express LHRH receptor, and that LHRH, LHRH agonists, and LHRH antagonists may have an effect upon uterine fibroids. See N. Chegini et al., “Gonadotropin-releasing hormone (GnRH) and GnRH receptor gene expression in human myometrium and leiomyomata and the direct action of GnRH analogs on myometrial smooth muscle cells and interaction with ovarian steroids in vitro,” J. Clin. Endocrin. Metab., vol. 81, pp. 3215-3221 (1996); and M. Marinaccio et al., “The estimation of LHRH receptors in the tissue of human leiomyoma, myometrium and endometrium,” Minerva Ginecol., vol. 46, pp. 519-526 (1994, English language abstract).